1. Field of the Invention
The present invention relates to a carburized component and a manufacturing method thereof.
2. Description of the Related Art
[Patent Reference 1]
Japanese Patent Publication No. H6-158266
[Patent Reference 2]
Japanese Patent Publication No. H6-25823
A gear as a mechanical transmission part of an automobile or the like is a part having problems of dedendum breakage occurring at a dedendum upon where bending stress acts, and breakage caused around a pitching point by sliding (pitching phenomenon). In order to satisfy characteristics capable of enduring these, a technique has been widely used to apply a carburizing process to a component surface so as to improve surface fatigue strength, and further improvement has been achieved by combining various kinds of materials and annealing. Also, recently a material has been developed in order to suppress a grain boundary oxidized layer and an abnormally-carburized layer when carburizing, which are considered harmful by causing dedendum breakage, and also further strength improvement has been achieved by shot-peening.
On the other hand, it's been revealed that when sliding repeatedly occurs on a gear tooth surface, the pitching phenomenon is caused mainly by frictional heat thereof increasing a temperature of an area directly below the tooth surface in a range of approximately 200° C. to 300° C., so as to cause softening of a quenched structure (martensite). Therefore, in order to improve pitching breakage, it is considered that it is effective to prevent a material from softening in a temperature range of approximately 200° C. to 300° C., and a material added Si, Mo, V or the like, as an alloy element having excellent softening resistance in this temperature range, has been developed.